The engineering stress-strain curve for ductile materials typically goes through a maximum. This maximum stress is the tensile strength of the material. Failure occurs at a lower stress after necking has reduced the cross-sectional area supporting the load. In more brittle materials, failure occurs at the maximum load, where the tensile strength and breaking strength are the same. In very brittle materials, including many ceramics, yield strength, tensile strength, and breaking strength are all the same.
The normal tensile test cannot easily be performed for many brittle materials because of the presence of flaws at the surface. Often, just placing a brittle material in the grips of the tensile testing machine causes cracking. These materials may be tested using the bend test. By applying the load at three points and causing bending, a tensile force acts on the material opposite the midpoint. Fracture begins at this location. The flexural strength describes the material's strength.
